Last Updated: Tuesday 17 April 2018

Amitabh Bachchan (in an advertisement) orders hot tea and snacks when his visiting friends tell him that it is blazing outside and they need something to cool down. Why? Because his air conditioner (AC) will freeze the room and people will want to drink hot stuff to stay warm. This is the problem of “wow” temperature that we undoubtedly suffer from. It’s not about comfort. It’s about status or something else.

This, when it is well-known that our cooling (and heating) machine is the key energy guzzler of our times. So, managing our cooling and heating needs would go a long way to reduce electricity demand and consequently carbon dioxide emissions that contribute to climate change. But we are still not getting it right.

What is a comfortable temperature that buildings should be designed to achieve? The Bureau of Indian Standards makes the National Building Code (NBC) that regulates building design in the country. It also defines the “comfort temperatures”. Its 2005 version had set 25-30°C for non-air conditioned buildings and 21-23°C for air-conditioned buildings for winter and 23-26°C for summer, which was widely seen to be too low.

So, based on this critique, the code was revised in 2016, but it has made things worse. The new NBC is so convoluted that instead of a number, you now have a formula. The formula defines what the internal temperature range should be in the building based on the outside mean temperature. It has also increased its typologies of buildings—naturally ventilated; mixed mode (where cooling or heating happens in certain areas or times) and only air-conditioned buildings. Then it has two categories of air-conditioned buildings. It is meant to confuse and confound and not to use.

I asked a colleague to calculate what would be the inside temperature defined by this code when the average outside temperature was 40°C? It turns out that in non-AC conditions, comfortable temperatures are up to 34.4°C, while in the AC conditions they are down to 25°C. The logic is rather strange—and definitely discriminatory. This so-called adaptive comfort model, which was derived from a study by the Ahmedabad-based CEPT University, crudely means that air conditioning is a factor of what human beings are used to in their lives.

NBC says, “People living year-round in air-conditioned spaces are likely to develop high expectations for homogeneity and cool temperatures, and may become quite critical if thermal conditions deviate from the center of the comfort zone they have come to expect. In contrast, people who live or work in naturally ventilated buildings are able to control their immediate interior spaces, get accustomed to variable indoor thermal conditions that reflect local patterns of daily and seasonal climate changes.”

In other words, the rich who are used to air conditioning would only be comfortable with lower temperatures as against the poor, who should be comfortable with higher temperatures, because their bodies have adapted to this.

This is the Indian form of socialism—it does not set the comfort conditions that all must aspire towards and ensure that all (including and especially) the rich are required to “adapt” to higher temperatures because of energy constraints. No, instead our government decides to ensure that the rich must use more energy because that is their comfort zone.

In contrast, Japan has mandated that that all office buildings and commercial establishments will not set their air conditioning below 28°C – this does not distinguish between the rich and the poor. This means that when temperatures are high outside and people are not in their “expected comfort zone”, they need to dress appropriately to get more comfortable. It does not mean that you allow the rich to guzzle more energy because that is what they are used to.

But let’s leave aside the question of this appalling system of setting temperature for comfort for the moment. What does comfort really mean? There are four variables for thermal comfort—temperature, humidity, heat radiation and air movement. Then of course, there are two critical human variables—clothing and an individual’s metabolism rate. In other words, you greatly increase comfort by designing spaces so that they reduce exposure to direct sunlight—radiant heat—and increasing ventilation. This means adopting the best practices of traditional (and poor peoples) buildings that were built on principles of passive architecture.

It means, first, designing buildings for the sun—literally. It means following the sun’s pattern so that you shade the building where the exposure to the harsh summer sun is the most extreme. This requires you to protect your building through shading devices—the common Indian chajja or canopy or balcony. This is what should be mandatory and not the sheer glass facades that our class conscious and air-conditioning loving rich love to build. It also means planting more trees on this summer side and better insulation.

But most importantly, it means that you need to ventilate the building because this is what brings the comfort—remember the poor who can adapt to higher temperatures. They did this because they build courtyards and designed their windows so that wind flow would be optimised. They designed for comfort.

It also means that we humans need ventilation to be comfortable. So, much more important than just setting the low temperature control is our lowly fan—also seen as the symbol of the poor’s comfort. Ironically, it is your fan that will make your comfort go up and not just your most expensive air conditioner. Let’s get really cool. And not just in the mind-conditioned way.

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Thanks for this very challenging and stimulating analysis! As I understand it, the "adaptive" model, which reflects comfort as experienced by people, is not challenged per se. We have no better theory right now. But the fact is, the revised NBC has gone, so to say, "half-way", on one hand recognising the notion of adaptive comfort BUT at the same time leaving almost undisturbed the bad habits that the AC industry has encouraged us to adopt. Historically, "comfort" has been the "product" that the AC industry is selling. The notion has been defined along commercial parameters, not scientific. Now, the "adaptive" theory explains us that the more we use AC the more we become sensitive to temperature variations, which is true and easy to verify. This is now the point where science alone can't help us. A blind application of "adaptive" theory will only justify and vindicate the bad habits induced by AC, by adding one more layer of "scientificity" to it, and even introducing a dual notion of "comfort for the rich" and "comfort for the poor" as Sunita Narain rightly points out. "Scientific facts" shouldn't be used as a cover for bad habits.

Can we throw the AC through the window? As an architect I don't think so. I have no AC in my home or office in Kolkata, because I have the luxury to live in a so-called "unplanned", "spontaneous" neighbourhood, away from the road, where a few trees have been allowed to survive, and in a house large enough to have a "summer office" and a "winter office". But I am more than happy that my doctor's chamber, or the tiny and overcrowded print shop, fully exposed to sunlight and a few feet away from a busy road, both have ACs!

This article is an open challenge to all of us to invent a new way to use AC. This involves architects, society at large, and even revising the notion of what we "purchase" exactly when we install and run a machine.

Thanks for this very challenging and stimulating analysis! As I understand it, the "adaptive" model, which reflects comfort as experienced by people, is not challenged per se. We have no better theory right now. But the fact is, the revised NBC has gone, so to say, "half-way", on one hand recognising the notion of adaptive comfort BUT at the same time leaving almost undisturbed the bad habits that the AC industry has encouraged us to adopt. Historically, "comfort" has been the "product" that the AC industry is selling. The notion has been defined along commercial parameters, not scientific. Now, the "adaptive" theory explains us that the more we use AC the more we become sensitive to temperature variations, which is true and easy to verify. This is now the point where science alone can't help us. A blind application of "adaptive" theory will only justify and vindicate the bad habits induced by AC, by adding one more layer of "scientificity" to it, and even introducing a dual notion of "comfort for the rich" and "comfort for the poor" as Sunita Narain rightly points out. "Scientific facts" shouldn't be used as a cover for bad habits.

Can we throw the AC through the window? As an architect I don't think so. I have no AC in my home or office in Kolkata, because I have the luxury to live in a so-called "unplanned", "spontaneous" neighbourhood, away from the road, where a few trees have been allowed to survive, and in a house large enough to have a "summer office" and a "winter office". But I am more than happy that my doctor's chamber, or the tiny and overcrowded print shop, fully exposed to sunlight and a few feet away from a busy road, both have ACs!

This article is an open challenge to all of us to invent a new way to use AC. This involves architects, society at large, and even revising the notion of what we "purchase" exactly when we install and run a machine.

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